1. Field of the Invention
The present disclosure relates to a drawing apparatus and an image forming apparatus that includes the same. More particularly, the disclosure relates to a drawing apparatus that draws a unit into an apparatus body, and an image forming apparatus that includes the same.
2. Description of the Related Art
Conventionally, an image forming apparatus such as a printer for forming an image on a sheet includes a unit mountable or drawable to and from a forming apparatus body (hereinafter, referred to as an apparatus body). As such units, for example, there are a sheet feeding cassette for receiving sheets, a sheet feeding device (sheet feeding unit) for feeding the sheets from the sheet feeding cassette, and an image forming unit (transfer unit or fixing unit) for forming images on the sheets.
When, after the units have been pulled out from the apparatus body, a user manually pushes the units into the apparatus body to load them on the apparatus body, sometimes the units may not be pushed and positioned into a loading completion position that is a predetermined position of the apparatus body. In the image forming apparatus, when the units are not set in the loading completion position of the apparatus body, various problems occur.
For example, when such a unit is a sheet feeding cassette, since a sheet is not in an appropriate position, an image may not be accurately formed on the sheet or a sheet feeding failure (skewed feeding or jamming of the sheet) may occur. When the unit is a transfer unit for transferring an image to the sheet, a position of the image may not be transferred to a correct position of the sheet, consequently causing an image quality failure.
Therefore, such units must accurately be positioned and loaded on the image forming apparatus.
Japanese Patent Application Laid-Open No. 2006-151687 discusses an image forming apparatus that includes a drawing mechanism for positioning a unit onto an apparatus body by using a toggle mechanism.
As illustrated in FIG. 15, a drawing apparatus 101 discussed in Japanese Patent Application Laid-Open No. 2006-151687 includes a toggle arm 106 configured to move around a swing shaft 107. At the swinging end of the toggle arm 106, a locking groove 106a is formed to lock a locking pin 102 of a sheet feeding cassette. Further, a toggle spring 108 is hung between a shaft 110 disposed in an apparatus body 51 and a shaft 109 disposed on the toggle arm 106 side. The drawing apparatus 101 further includes a guiding member 111 disposed to lock and guide the locking pin 102.
When the sheet feeding cassette is inserted into an accommodating unit 1B of the apparatus body 51, as illustrated in FIG. 16, the locking pin 102 of the sheet feeding cassette is locked into the locking groove 106a of the toggle arm 106, and the sheet feeding cassette is drawn to a sheet feedable position by the drawing apparatus 101.
A pressing direction of a spring force applied by the toggle spring 108 is reversed from a clockwise direction to an anticlockwise direction at a neutral point. Before its insertion, the sheet feeding cassette stands by in a position near the neutral point, in a slightly shifted phase from the neutral point, and is pressed in the clockwise direction.
Then, when after the insertion of the sheet feeding cassette, the locking pin 102 is locked in the locking groove 106a of the toggle arm 106, and the toggle arm 106 is swung beyond the neutral point, the pressing force of the toggle spring 108 is revered in the anticlockwise direction, and the cassette is drawn into the apparatus body.
However, the drawing apparatus using the toggle mechanism needs the swinging member for changing the direction of the pressing force applied by the toggle spring and the guiding member for guiding the locking member locked in the swinging member.
Specifically, the drawing apparatus using the toggle mechanism illustrated in FIG. 16 needs the toggle spring 108, the toggle arm 106 for grabbing the locking pin 102 to draw the sheet feeding cassette, and the guiding member 111 for guiding the locking pin 102 locked in the locking groove 106a of the toggle arm 106.
However, greater cost reduction is demanded for the recent image forming apparatus. There is a demand for an apparatus small in a number of components, simple in configuration, and capable of surely positioning units in an apparatus body.